ABSTRACT
When Faraday first measured a semiconductor, the distinguishing feature was the fact that the conductance actually increased with temperature, rather than decreased as expected for the well-known metals (Faraday, 1833, 1834; Martin, 1932), The discovery of photoconductivity (Smith, 1873) and rectification (Braun, 1874) provided still further effects unheard of in metals. All of these effects together suggest that the important major difference between semiconductors and metals is the presence of the energy gap in the spectrum of the semiconductor. The increase in conductance with temperature arises from the thermal excitation of an increasing carrier density across the energy gap.
